XC

Description

XC is a module for APIcast, 3scale's API Gateway. APIcast performs one call to 3scale's backend for each request that it receives. The goal of XC is to reduce latency and increase throughput by significantly reducing the number of requests made to 3scale's backend. In order to achieve that, XC caches authorization statuses and reports.

The current version works with APIcast v.3.0.0-rc1

Development environment and testing

You will need Docker and GNU make.

First, clone the project:

$ git clone [email protected]:3scale/apicast-xc.git

Next, cd into the directory, cd apicast-xc

Run the tests with:

$ make test

That will run the unit test suite and also a code linter inside a Docker container. The unit tests suite uses Busted. For code linting we use Luacheck.

Develop:

$ make bash

That will create a Docker container and run bash inside it. The project's source code will be available in ~/app and synced with your local apicast-xc directory. You can edit files in your preferred environment and still be able to run whatever you need inside the Docker container.

How it works

XC uses Redis as a cache to reduce the number of queries to the 3scale backend. When a requests comes in:

• If the authorization is cached:

  1. The authorization status is retrieved from Redis.
  2. If the request is authorized, the usage report is cached in Redis and will later be send to 3scale backend in a batch.
  3. XC returns authorized/denied to the Gateway.

• If the request is not cached:

  1. The authorization status is retrieved from 3scale.
  2. The authorization status is cached in Redis.
  3. If the request is authorized, the usage report is cached in Redis and will later be send to 3scale backend in a batch.
  4. XC returns authorized/denied to the Gateway.

XC only takes care of the Redis accesses part. To work correctly, it needs to be deployed along with xcflushd. xcflushd is a daemon that basically takes care of:

1. Reporting the cached reports in batches.
2. Updating the status of the cached authorizations.
3. Retrieving an authorization status from 3scale backend when it is not cached.

For further details about xcflushd, please go to its GitHub repo. For a more detailed explanation about how XC works, please check this design doc.

Deployment

At the moment, deploying APIcast with XC is not as convenient as we would like. We are currently working on offering an easy way to deploy it on Openshift.

In the meanwhile, you can use Docker or deploy XC locally. Deploying APIcast with XC is very similar to deploying APIcast. The only difference is that XC needs two environment variables not required in APIcast:

APICAST_MODULE=apicast_xc
XC_REDIS_HOST=your_redis_host.com:6379

Optionally, you can also configure other options of the redis pool with these environment variables:

• REDIS_TIMEOUT (in milliseconds)
• REDIS_KEEPALIVE (in milliseconds)
• REDIS_CONN_POOL(number of connections in the pool)

Docker

Build the image:

$ docker build -t apicast-xc -f Dockerfile-apicast .

Run:

$ docker run --name apicast --rm -p 8080:8080 -e XC_REDIS_HOST=your_redis_host.com:6379 -e APICAST_MODULE=apicast_xc -e THREESCALE_PORTAL_ENDPOINT=https://[email protected] apicast-xc

Locally

• Run make apicast.xc to install XC's dependencies.
• Copy apicast_xc.lua and the xc directory of this repo into the src directory of APIcast.

APIcast can then be executed like this:

$ XC_REDIS_HOST=your_redis_host.com:6379 APICAST_MODULE=apicast_xc THREESCALE_CONFIG_FILE=config.json bin/apicast

For a more detailed explanation about deploying APIcast and running it, please check its GitHub repo.

Remember that you'll also need xcflushd running.

Trade-offs

Compared to APIcast:

Pros

• Considerably lower latencies and higher throughput.
• If 3scale is unreachable, applications can still be authorized using the cache.

Cons

• Needs two extra components to work: Redis and the flusher.
• Going over the defined usage limits is easier. APIcast reports to 3scale every time it receives a request. Reports are asynchronous and that means that we can go over the limits for a brief window of time. On the other hand, XC reports every X minutes (configurable) to 3scale. The window of time in which we can get over the limits is wider in this case.

Limitations

These are some of the current limitations. They will be fixed if there is a need.

• XC can only hit one application per request.
• The timestamp of the reported transactions loses resolution. Transactions are assigned a timestamp when they are reported to 3scale. With APIcast this happens in every request. On the other hand, with XC this happens when the flusher sends the reports. This happens every X minutes (configurable).

Contributing

1. Fork the project
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes: git commit -am 'Add some feature'
4. Push to the branch: git push origin my-new-feature
5. Create a new Pull Request

License

Apache-2.0